ABSTRACT
This chapter summarizes some of the emerging concepts concerning the anatomy and function of intrathoracic afferent, efferent, and local circuit neurons involved in cardiac regulation as well as some of the possible interactions that may occur between them. Intrathoracic vascular mechanoreceptors appear to be length-sensitive receptors and are located on the vena cavae, pulmonary arteries, pulmonary veins, all along the thoracic aorta, and on the major arteries arising from the aorta. Cardiovascular-related activity of intrathoracic local circuit neurons sometimes also occurs during every other beat when pulsus alternans is present. Some intrathoracic efferent sympathetic neurons are activated via reflexes following distortion of mechanoreceptors in limited regions of the heart or great thoracic vessels. Physiological evidence has implicated intrathoracic local circuit neurons in cardiac regulation. Although a number of authors have described the presence of neurons on mammalian hearts, including the human heart, little is known about their function.
